FACTS OF LEECH

Leeches are ‘worms’ with suckers on each end. Leeches can range in size from from a half of inch to ten inches long. They are green or black in colour. Some feed on decaying plant material. Others are parasites, feeding on blood and tissue of other animals. The one that typically is feeded is Hirudo Medicinalis
Blood-sucking leeches suck your blood in two ways: they use a proboscis to puncture your skin, or they use their three jaws and millions of little teeth. They live just about anywhere there is water. Leeches find you by detecting skin oils, blood, heat, or even the carbon dioxide you breathe out.
Leeches do not feed often. That is because they take in a lot when they do feed.
Doctors often used leeches in the past to draw blood. Some barbers used to do surgery as well as cutting hair, and they used leeches. When a barber finished surgery, he took the bloody bandage and wrapped it around a pole to show he did surgery, too. That’s how the white and red swirled barber pole came to be.
Today, maggots and leeches are being used for different reasons. Scientists are studying leech saliva. They believe the substance that stops or prevents blood clots will one day be able to be used on humans. Researchers have also identified several medical compounds which can be developed from leech saliva. The anticoagulant and clot-digesting properties of these substances make them potentially useful as drugs for the treatment of cardiovascular diseases such as heart attacks and strokes. Leeches can be “milked” for their secretions without being harmed, and research is continuing into the possibility of synthetically engineering leech saliva.
And leeches are still being used to suck blood! Doctors are now turning to leeches to help restore blood circulation to grafted tissue and reattached fingers and toes. In 1985, microsurgeons in a Boston hospital used leeches to save the ear of a 5 year old boy that had been bitten off by a dog. The leech can remove any congested blood to allow normal circulation to return to the tissues, thus preventing gangrene from setting

Respiration
Respiration takes place through the body wall, and a slow undulating movement observed in some leeches is said to assist gaseous exchange. Aquatic leeches tend to move to the surface when they find themselves in water of low oxygen content. As a fall in atmospheric pressure results in a small decrease in dissolved oxygen concentrations, rising leeches in a jar of water provided nineteenth century weather forecasters with a simple way of predicting bad weather.
Sense Organs
Sensory organs on the head and body surface enable a leech to detect changes in light intensity, temperature, and vibration. Chemical receptors on the head provide a sense of smell and there may be one or more pairs of eyes. The number of eyes and their arrangement can be of some use in Identification, however to properly identify a leech, dissection is required.

Reproduction
As hermaphrodites, leeches have both male and female sex organs. Like the earthworms they also have a clitellum, a region of thickened skin which is only obvious during the reproductive period. Mating involves the intertwining of bodies where each deposits sperm in the others' clitellar area. Rhyncobdellids have no penis but produce sharp packages of sperm which are forced through the body wall.
The sperm then make their way to the ovaries where fertilisation takes place. The clitellum secretes a tough gelatinous cocoon which contains nutrients, and it is in this that the eggs are deposited.
The leech shrugs itself free of the cocoon, sealing it as it passes over the head.
The cocoon is either buried or attached to a rock, log or leaf and dries to a foamy crust. After several weeks or months, the young emerge as miniature adults. Studies show that the cocoons are capable of surviving the digestive system of a duck. Leeches die after one or two bouts of reproduction.